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If a read/write expanded variable is declared locally to the assignment statement that is updating it, and it is referenced exactly once in the assignment RHS, then we can optimize the operation as a direct update of the expanded value, whether or not the function(s) operating on it can be trusted not to modify the value before throwing an error. This works because if an error does get thrown, we no longer care what value the variable has. In cases where that doesn't work, fall back to the previous rule that checks for safety of the top-level function. In any case, postpone determination of whether these optimizations are feasible until we are executing a Param referencing the target variable and that variable holds a R/W expanded object. While the previous incarnation of exec_check_rw_parameter was pretty cheap, this is a bit less so, and our plan to invoke support functions will make it even less so. So avoiding the check for variables where it couldn't be useful should be a win. Author: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: Andrey Borodin <x4mmm@yandex-team.ru> Reviewed-by: Pavel Borisov <pashkin.elfe@gmail.com> Discussion: https://postgr.es/m/CACxu=vJaKFNsYxooSnW1wEgsAO5u_v1XYBacfVJ14wgJV_PYeg@mail.gmail.com
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.